Physical considerations:
On engines with throttle valve control, the throttle valve is slightly open in the idling and part-
load ranges. This results in the formation of up to 500 mbar vacuum in the intake manifold,
which prevents the engine from aspirating freely and in turn prevents optimum cylinder fill-
ing. The Valvetronic system with an open throttle valve largely counteracts this disadvan-
tage. The air-mass flow to the intake valves is unrestricted. The full ambient pressure is
available directly at the intake valves for cylinder filling and scavenging.
The Valvetronic system primarily controls the fill by adapting the valve opening time and the
valve lift (short opening time/small valve lift = lower fill, and vice versa). During the valve
opening phase the engine aspirates more freely via the intake valves even with small valve
lifts vs. a throttle valve which is continuously blocked.
The slower cylinder filling from the intake valves with partial lift results in more turbulence in
the combustion chamber, thus faster and better mixture control and more efficient com-
bustion. At lower engine speeds this effect is intensified by opening the intake valves later,
after top dead center (ATDC) using VANOS. This increases vacuum in the combustion
chamber which accelerates filling and turbulence when the intake valves are opened.
IInn ssuummmmaarryy,,
the additional variability of the Valvetronic system results in optimization of
cylinder filling and scavenging throughout the engine's entire operating range. This has a
positive effect on output, torque and a decrease in fuel consumption and exhaust emis-
sions.
FFeeaattuurreess::
• Valve lift adjustment
• VANOS for intake and outlet
• Variable intake manifold
• Mixture control and ignition control
• Other individual engine design measures
TThhiiss rreessuullttss iinn::
• Improved engine idling
• Improved engine torque
• Improved engine torque curve
• Fewer pollutant emissions
TThheessee bbeenneeffiittss rreessuulltt iinn aa cclleeaarr iimmpprroovveemmeenntt iinn ppeerrffoorrmmaannccee aanndd ffuueell ccoonnssuummppttiioonn rreedduucc--
ttiioonn ((1144%%)) ffoorr tthhee ddrriivveerr..
24
N62 Engine
TThhee mmaaiinn bbeenneeffiittss ooff tthheessee ffeeaattuurreess aarree::
• Improved cylinder filling with air/fuel mix-
ture
• Improved mixture control before the cylin-
der inlet
• Improved combustion procedure
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